welcome egregor1
I don't have a list stating all error messages, but at first I advise you to upen up the red hood and check all the cables inside the Electro. To open up unscrew the wooden sides, the screws at the back and some of the large ones at the bottum of the instrument. It doesn't happen often to the Electro, but due to transport, special to gigs, cables tend to get unconnected. Check it all.
Wout